Shielded enclosures or screen rooms are utilized to shield electrical equipment which may cause interference with other equipment as with radio receivers and the like. This is particularly true where the equipment may emit high frequency interference. Further screen rooms are used for security purposes where it is important that equipment contained within the room will not be subjected to "electronic eavesdropping".
Such rooms or enclosures may be fairly large and usually include shielding material, i.e. metal plate, extending over the interior and outer surfaces of wall members making up the room or enclosure. Because these metal plates may comprise a large area, they are subjected to appreciable thermal expansion and contraction due to temperature changes. Such relatively large thermal expansion and contraction may result in considerable relative movement in joint areas formed by adjacent plates in turn effecting R.F. seal integrity.
Any spacing in thermal expansion joints between adjacent wall members requires that an effective electrical seal be maintained between the shielding of adjacent wall members. Conventionally such a seal utilizes strips of finger stock material which comprises a plurality of adjacent curved metallic fingers which are connected at one end to a strip which is in turn connected to the shielding of one wall member while the curved portions of the fingers contact the shielding of an adjacent wall member. The result is that the fingers form an electrical seal between the shielding of the two wall members while at the same time allowing for relative movement between the two wall members. Such conventional strip material is generaly fragile and fingers comprising the finger strip material may be broken off or bent out of shape if movement between the wall members becomes misaligned. Specifically if the gap or spacing between the relative movable wall members due to any misalignment becomes too great, the fingers may not be able to expand sufficiently to contact the shielding of an opposite wall member, or if due to misalignment the spacing between two wall members becomes too narrow, the fingers may be crushed or torn away. In either event the effectiveness of the RF shield is diminished.
It is therefore an object of my invention to provide for an RF expansion joint between two relatively movable wall members which will assure that the wall members will always remain in proper alignment to prevent any impairment of an electrical seal between the two members because of destruction of the seal material or due to failure of the seal material to contact the shielding material of the two wall members because of misalignment.